FREETOWN, Sierra Leone — Liberia is making some progress in containing the Ebola outbreak while the crisis in Sierra Leone is going to get worse, the top anti-Ebola officials in the two countries said.

International assistance is still desperately needed and the people of both countries must redouble efforts to stop the disease, which has infected more than 13,000 people and killed nearly 5,000, the officials said.

Their assessments underscore that Ebola remains a constant threat until the outbreak is wiped out. It can appear to be on the wane, only to re-emerge in the same place or balloon elsewhere if people don’t avoid touching Ebola patients or the bodies of those who succumb to the disease.

To help respond to the growing crisis in Sierra Leone, a British naval ship, carrying hundreds of troops, medical supplies, helicopters and trucks, docked in the capital on Thursday.

“With all these facilities, they will go a long way in the ongoing fight against the Ebola disease,” Alfred Palo Conteh, the new head of the country’s National Ebola Response Center, said Thursday, as he greeted the arriving ship.

On Wednesday, Conteh had warned that more needed to be done.

“We are in a crisis situation which is going to get worse,” Conteh told reporters. “What is happening now should have been done three months ago.”

The stark warning and call to action were echoed by others, even in neighbouring Liberia, where the World Health Organization has said the rate of infection appears to be slowing, perhaps by as much by 25 per cent week over week.

The WHO announcement has given Liberia a reason “to put our shoulders to the wheel so that Ebola can be something of the past,” Deputy Information Minister Isaac Jackson told a news conference Thursday. “We are not going to relax.”

World Health Organization officials also urged caution in giving the news, saying the gains could be reversed.

But others went further. Alfred Brownell, an activist in Liberia, remembered the moment in the spring when Liberians thought the crisis was over, but then it got worse. Now he is bracing for another potential wave of cases, he said.

“The present epidemic is unpredictable: We have seen a lull in cases in one area only to see the numbers spike again later. More aid is needed on the ground. It’s time now to step up contact tracing, safe body management practices and community surveillance,” said Fasil Tezera, head of Doctors Without Border’s mission in Liberia, even while noting that their 250-bed centre in the capital has only about 80 beds occupied.

Liberia is the hardest hit country in the Ebola outbreak sweeping West Africa that has also ravaged Guinea and Sierra Leone.

Still, there are some signs of hope. In Liberia, there has been a decrease in the number of patients seeking Ebola treatment, the number of bodies collected and the number of lab-confirmed cases, according to Nyenswah.

In Sierra Leone, even though the outbreak is now hitting areas in and around the capital, the country’s east has seen the disease wane. Conteh, the country’s top anti-Ebola official, urged people to follow the example of Kailahun and Kenema Districts, by not touching the sick or dead.

He added that international assistance is growing: Up to 700 beds will be set up in treatment centres and the United Nations has four helicopters in the country.

The British ship the Argus docked Thursday in the country carrying 300 military personnel, 32 pick-up trucks, three helicopters, and medical and other supplies. Although it has a hospital on board, it will not accept patients on this mission. Instead, it will serve as a hangar and take-off and landing zone for the helicopters. The helicopters will ferry supplies and people to hard-to-reach areas of the country, said Commanding Officer Ross Spooner.

The outbreak has taken a particularly high toll on health workers, sickening more than 520, and greatly reducing the health system’s capacity to respond in the three most-affected countries.

The World Bank announced Thursday that it will give an additional $100 million to help bring in more foreign health workers. The new funds will be used to train, pay and house health workers while they’re in the Ebola hot zone and provide medical care or evacuation for anyone infected.

If the virus continues to surge in the worst-affected countries and spreads to neighbouring countries, the financial impact could reach $32.6 billion by the end of 2015, the bank has warned.